To many, Mackintosh is well regarded as one of the most influential-- if not the most influential-- comparative psychologists of his generation. His 1974 textbook The Psychology of Animal Learning is still considered to be the greatest book ever written on the subject. The latter few decades of his life he became interested in IQ and human intelligence, and his textbook IQ and Human Intelligence is also the best textbook ever written on the subject.

But to me, and many of his other students, friends and colleagues, he was Nick: a warm, generous, wise and powerful mentor.

I first met Nick in 2001 when I was a wee undergraduate. The pain and suffering I experienced as a child after being labeled with a learning disability and being treated as such, led me to become fascinated with intelligence and human potential. Sophomore year of college I discovered there was an entire field of scientific investigation dedicated to understanding the mechanisms of intelligence. I decided to take a semester leave of absense from Carnegie Mellon and learn as much as I could about this fascinating field. In my search, Nick's name came up as a leading expert on intelligence. Only catch: he was head of the experimental psychology department at University of Cambridge in England.

Common doubts surfaced. What if I’m not smart enough for this? This is Cambridge, for heaven’s sake. What if he gives me an IQ test? What if he asks to see my standardized test scores?

I eventually sucked it up and emailed him. To my surprise, this esteemed Professor responded almost immediately with an open heart and extended an invitation for me to work with him for an entire semester.

When I arrived in Cambridge in 2001, humbled by spires, ivy and stained glass windows, I was convinced that IQ tests are worthless. I thought I was going to learn that they don't measure intelligence whatsoever. Instead, what I gained from the experience was much more valuable. I learned the value of scientific humility.

Conducting research with Nick on IQ, I found evidence firsthand that various cognitive abilities (e.g., verbal, visual, spatial) are indeed positively correlated with each other: those who are good at one test tend to be good at the others, and those who are poor at one test tend to do poorly on the others. But I also learned that these abilities are also at least partially separable. We conducted some studies on mental visualization ability and found that it certainly does have unique predictive validity above and beyond global IQ scores.

Taking Nick's course for undergrads also taught me that there are multiple potential causes of these positive correlations among varous cognitive abilities. Nick's balanced, measured, open-minded, charismatic, and reasonable lectures inspired me to want to learn more about intelligence. Soon all of my prior preconceptions about IQ disappeared, and what emerged was an even greater thirst for understanding. I'm not sure many other scientists could have done that for me, considering how confident I was about IQ before I stepped foot in Cambridge.

In an article published in 2013, Nick addressed the question: "Why Teach Intelligence?". In this terrific article, Nick makes a persuasive case for the value of teaching human intelligence. He writes:

"IQ tests are one of psychology's more visible and controversial products. For this reason alone, a student who has graduated with a degree in psychology ought to know enough about the subject to dispute some of the public's misconceptions. Controversey breeds disagreement, and although intelligence researchers are agreed on some of the conclusions suggested by their research, they disagree strongly about others. One reason is that many see desireable or undesireable implications of such research, and their evaluation of the research is influenced by those perceived implications. Another is that the nature of intelligence research, where well-controlled experiment is usually not possible, and conclusions are based on mere correlations or the results of necessarily ill-controlled natural experiments, means that not all conclusions are unequivocally dictated by the evidence. For these reasons an advanced course on human intelligence can teach a student how to evaluate necessarily ambiguous evidence, without being swayed by his or her prior beliefs or wishes."

I would eventually go on to study with Nick for a Masters degree, and then collaborate with him on my PhD study on the relationship between IQ and implicit learning. Just a few years ago, while I was working on a book on intelligence, I spent a summer in Cambridge and Nick offered me feedback. We would meet and discuss his comments on a chapter-by-chapter basis, and I made sure I told him how much his constant support and good example meant to me. I remember one particularly poignant moment when I broke out in tears telling him how much his support has meant to me, and even in his typically measured British gentlemanly fashion, I could tell my words meant a lot to him.

Yes, Nick was a connsumate scientist. But he was that rare combination of scientist who was also a wonderful mentor, and a human being with great humility. This can clearly be seen in this video from 2013, in which he is honored by the International Society for Intelligence Research:

In this video, I really enjoyed hearing about Nick's nontraditional path to becoming a psychologist, and agree with his call for more research on the causes of the emergence of the general intelligence factor, its relationship to executive functions, and the important distinction between explicit and implicit learning. But that's not what strikes me the most in this interview.

At one point, Nick is asked who his heroes are in his professional life. In response, he mentions one of his own mentors, Stuart Sutherland. As Nick notes, Sutherland "treated me as an equal, even as an undergraduate." This must have made quite an impression on Nick, and most certainly influenced him to treat other students, including myself, as an equal. Even when I was an undergraduate.

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